My Dax Gen IV was a major disappointment. I put my old motor back on.
Save your money. It did not feel any smoother than my 3 year old ebay motor.
Read my post
"Dax GenIV balanced bottom issues and questions" and decide for yourself.
http://motorbicycling.com/showthread.php?p=550104
Mine probably got less than 10 miles on and now is sitting in a box under the work bench.
My dax Gen IV is the smoother of my engines and with the port work I did on the jug it is also the fastest, very noticeably smoother than all my other engines, I have twisted it up to 9400rpm and it just sings....
I have two more of the dax lowers I plan to build to replace a couple other of my engines, your issue is the first I've heard of, all the other experiences I have heard of have been just like mine.
Dang that stinks and you must have got a lemon... I'd holler at Duane over at thatsdax and ask him if he would be willing to work with you getting another, you must have got one with a really untrue crank or something.
I love mine, and as a matter of fact I just got mine mounted back on my bike today, I har broke a rear stud and wanted to clean the engine and paint it up nice so I did all that today and took a ride after dark, I weigh 220lbs and im running a 28T rear sprocket on a 26" wheel, that was another change I made to the bike today, not sure yet how well the small sprocket is gonna do for me, seems to pull it pretty nice, but I may have to go up to a 30T to get it where ai want it, time will tell but my dax engine has a lot of power even with that samll of a sprocket, I was surprised...
Map